This invention relates to a process for stabilizing the viscosity of chloroprene polymers and polymer blends.
Chloroprene polymers suitable in the process of this invention are homopolymers of chloroprene and copolymers of chloroprene with ethylenically unsaturated organic monomers, including copolymers of chloroprene with sulfur, the so-called sulfur-modified chloroprene polymers. Chloroprene polymers are often compounded at elevated temperatures, of the order of 100.degree.-120.degree. C. or higher, in mixing or blending equipment such as internal mixers or rubber mills, frequently under high shear conditions. Mastication or shearing at elevated temperatures generates free radicals, which are capable of attacking the polymer backbone and causing crosslinking of the polymer. Sulfur-modified polymers often increase in viscosity during ambient temperature aging. These changes are, of course, undesirable because they result in loss of processability and also in deterioration of physical properties of the vulcanized elastomer.